In a traditional server tape backup system, a backup server moves data from one or more application servers to a set of tape drives based on a backup schedule. Once a backup event has been completed, the tapes on which the backup has been made are transferred to a tape vault, where they are physically archived. In the event of a system failure, or data loss, data may be restored from the tape vault to an application server. This process involves physically searching the tape vault to identify the correct restore point, transporting the appropriate tape back to the server room, and restoring the appropriate data. Due to the number of steps involved, this type of restore process can take several hours and, in some cases, even longer. This extended length of time can be unacceptable in highly available systems.
Virtual tape libraries are increasingly being used to supplement traditional tape libraries with the primary purpose of reducing the time that is required to restore the contents of a backup tape. In a virtual tape library, a disk array replaces the tape library. The disk array exposes a storage area network interface through which a backup server may connect to it. Each tape drive of the tape library is replaced by a volume, which is exposed as a storage target. The application servers connect to their corresponding targets and proceed to back up data under the direction of the backup server. Since disk technology is faster than tape technology, a well-designed virtual tape library can offer superior performance to a tape for backup, and performance that is orders of magnitude higher for the restoration of backed up data. However, current virtual tape libraries still suffer from performance limitations during normal operation and also during anomalous situations, such as drive failure.
It is with respect to these considerations and others that the present invention has been made.